11:45 a.m.: Are they expecting the Normandy invasion? Lollapalooza officials say that security has been beefed up to prevent gate-crashers, a big problem at last year’s festival, and the main entrance is blocked off with fencing, roadblocks and lots of beefy personnel to discourage any sort of rogue behavior. Shelby Meade, media liaison for promoters C3 Presents, amplifies: “We increased the amount of ‘black fence’ we're using, but we're also doubling our fencing in some spots. You'll notice we are still utilizing chain-link fencing, but we have installed additional black fencing behind some of that, particularly along Lake Shore Drive and the outer perimeter of the park. There is also chain-link fencing on the east side of Lake Shore Drive.” She adds that fans trying to cross Lake Shore Drive, a major breach point last year, will be redirected to crosswalks at the Field Museum and Monroe Street. (GK)

12:01 p.m.: U.K.trio Animal Kingdom gets things rolling. “This our first time at Lollapalooza, our first time playing an American festival, our first time playing in America, really,” says singer-guitarist Richard Sauberlich. Right down to the high, fragile vocals and gauzy guitars, the band comes off as Radiohead-lite. Thom Yorke has inspired a generation of singers, it seems, and there’s no end in sight. (GK)

12:16 p.m.: Klara Soderberg sings about broken hearts as her whippoorwill voice breaks them. She and sister Johanna comprise First Aid Kit, and together, their close high harmony vocals and soulful folk result in the best opening performance at Lollapalooza that I've ever seen. Adorned in traditional, hand-sewn European dresses, and swaying to and fro, the Swedish duo isn't all sugar and spice. Dark undercurrents travel amid the mellow roots arrangements and storytelling. A drummer supplies train-song backbeats and occasionally taps out xylophone accents. The percussive foundations work well, yet the focus remains on the siblings' meticulous, lilting songcraft. Nothing is over- or under-done. As Johanna hovers around her keyboard, Klara strums an acoustic guitar and takes a moment to talk of the group's appreciation for Johnny Cash, June Carter Cash, Gram Parsons and Emmylou Harris. Their knowledge of Americana history becomes evident with each successive tune. A cover of Fever Ray's "When I Grow Up" precedes a snarling "The Lion's Roar," which finds Johanna stomping her clogs on the stage floor and thrashing her long hair in slow motion, possibly in tribute to her native country's renowned metal acts. (BG)

1:02 p.m.: Lines for water refilling stations are three dozen people deep. Is it too late to add more for the weekend? (BG)

1:13 p.m.: Brazilian band O Rappa salts its heavy reggae beats with salsa and hip-hop breakdowns. For about a dozen minutes, all signs are pointing up. But a cover of garage-rock nugget “Hey Joe” sounds a bit perfunctory, as if the band doesn’t trust its homegrown material to translate to the mostly Caucasian audience. A later digression into Deep Purple’s “Smoke on the Water” comes off as pure desperation. (GK)

1:52 p.m.: Michael Kiwanuka starts his set in a casual, jazz-folk direction. All that’s missing are wind chimes and incense. A cover of Jimi Hendrix’s “May This Be Love (Waterfall)” fits just right. The U.K. singer is a modest sort who strives to make his performance feel smaller, more intimate, rather than trying to push his music and personality outward. He focuses on tiny details – the tapping of a triangle, the brush of fingers on guitar strings – and then patiently builds them into something more substantial. (GK)

1:56 p.m.: In what might be a Lollapalooza first, a man proposes to his girlfriend onstage and she accepts. It's by far the most exciting point during Yellow Ostrich's otherwise perfunctory set. Led by guitarist/vocalist Alex Schaff, the New York indie trio isn't primed for the big stage. Songs stumble and lurch, and while Schaff owns a few cool effects pedals that add kick, they're not enough to compensate for off-centered fare such as "Elephant King" that never gets out of second gear. Whiny vocals and cutesy lyrics don't help matters. (BG)

2:19 p.m.: It’s a sunny afternoon, but the Black Angels don’t want any part of it. They focus on the three D’s -- doom, drone and distortion – and bring them raining down accompanied by tribal rhythms. The band knows how to hang on a riff until it turns stark and forbidding. “It’s hard to kill when you don’t know what side you’re on,” they sing. The Texas band fills the northern end of Grant Park with darkness. But the set could use more variety, a few rave-ups to keep the tunes from melting together. (GK)

2:21 p.m.: "[Stuff] is vibrating up here." Alex Granduciel, front man for the War on Drugs, stacks layers upon layers of sound, so the frequency effects aren't surprising. The Philadelphia quartet prizes droning expanse and atmospheric heft. Songs evoke the feeling of long highway trips, with Granduciel's nasal drawl coming on as the equivalent of the observations of someone who's spent far too long sitting in a touring van. Travel and distance prominently figure into the narratives. "Coming Through" spotlights the band's surrealist qualities and preference for sticking to a steady groove. Random harmonica passages and horn phrases augment the psychedelia, yet the group's sun-warped trance avoids one-dimensional jams and conveys thickness without ever turning heavy. "I'm always drifting,” Granduciel sings, and one doesn't doubt the admission serves as his motto. (BG)

3:23 p.m.: "I'm not going any further until I see everyone's hands up," announces Zedd, a k a Anton Zaslavski. The German producer/deejay's statement is no more than an idle threat. Perched atop a large platform, he mixes spoken catch phrases with hyperactive electrohouse, spurring the crowd to rapidly jump, toss projectiles, wave flags, hoist inflatables and spin umbrellas in the simmering heat. Strobe lights flash and momentum builds, recedes and builds again. Still, Perry's stage isn't what it was. By removing the tent-like canopy, organizers significantly increased capacity at the expense of sacrificing atmosphere. There's a loss of intimacy and community, and the visuals get washed out by the sunlight. Most don't notice. Zedd activates overdriven synthesizers and familiar samples to keep the party going, and Perry's unofficially takes over as Chicago's largest singles bar for the next few days. (BG)

3:39 p.m.: First Aid medics refuse to disclose what kinds of injuries and illnesses they are treating, but in judging from the requests of people stopping at the tent, band aids for blisters seem to be in great demand. As does water. Already exhausted, people are camped under trees, with their head between their legs. (BG)

3:41 p.m.: Sharon Van Etten talks amiably to her admiring fans between songs. But the songs themselves are loaded with melancholy, the sense that even the best of times with a lover aren’t destined to last. Her wordless harmonies with keyboardist Heather Broderick are even more expressive than Van Etten’s lyrics. But on “Serpents,” Van Etten lets her guitar do the talking, generating a cyclone of resentment. The singer has come a long, long way since she opened the Pitchfork Music Festival a few years ago as a solo act. She and her band are a formidable combination. (GK)

4:37 p.m.: “I’m a gentle man,” Greg Dulli insists. But the characters in his songs know better. Dulli has reunited with his ‘90s band, the Afghan Whigs, and the expanded six-piece lineup dresses in black to match the mood in the vast majority of their songs. Few bands luxuriate in cruelty and coldness as extravagantly as the Whigs. Their night-life visitations remain as harrowing as any ever recorded, and Dulli still sings like his head is about to explode, the veins popping in his neck as he reaches for a note just beyond his reach. A cover of Frank Ocean’s “Lovecrimes” finds Dulli at the keyboards, clearly enamored with a contemporary kindred spirit. The only disappointment perhaps is that Ocean himself doesn’t appear. No matter, Ocean will get his turn Saturday. This afternoon belongs to Dulli and his Whigs cofounders John Curley and Rick McCollum, who sound as commanding as ever. (GK)

5:08 p.m.: More cowbell! London's SBTRKT pulls out the famed clanking instrument to further color its highly rhythmic melange of two-step, pop, minimalist electronica and funk. And what a difference live drumming and vocals make. The duo, fresh from stepping off the plane, could easily be playing Perry's with a bevy of other electronic-minded artists. Instead, the group's organic approach gives compositions such as "Hold On" and "Wildfire" a rawness and tangibility missing from the artificially processed output of its peers. Aaron Jerome keeps one hand on the knobs of a control board and the other on his drum stick. Partner Sampha hops across the stage and lends R&B pipes to a majority of the material. SBTRKT claims a nuanced, textured feel that's often altogether missing from club-ready music. Bongos, wheezing synths and hi-life beats flavor the worldly vibes. This is about dazzling, not dizzying the senses, and the show is all the better for it. (BG)

5:35 p.m.: The hootenanny bands are proliferating, from Mumford & Sons to the Lumineers. They play acoustic instruments, they clap hands and lead exuberant sing-alongs. Often, they wear suspenders. The Head and the Heart are yet another band of hootenanny folkies, who at times suggest a vaudeville act run amok. The band’s feel-good vibe works well enough in the late-afternoon sun, but the songs feel slight, the inclusiveness a bit forced. (GK)

5:55 p.m.: The band led by Dhani Harrison – Beatle George Harrison’s only son – calls itself thenewno2, after a character in the cult British TV series “The Prisoner.” Harrison’s dry, droll voice resembles the old man’s, but little else in his musical arsenal does. With his band he creates dense, layered songs, which owe as much to electronic music as they do rock. On record, the music can feel a bit tame, but live it expands. The art songs grow bolder, and Harrison’s understated charisma becomes more of a focal point. (GK)

6:02 p.m.: Instant energy. DJ Porter Robinson immediately demonstrates why he's among today's hottest remixers and producers by serving up volleys of low-end, teeth-rattling bass bursts and spitting, quick-hitting drum fills. He inserts clever spoken commands into the glitchy collages, producing "complextro" sequences that rely on repetition and soft-to-loud surges for which the audience waits in anticipation. A fan holds a large sign: "Drugs I'm not on," underneath which he's listed just a few select pharmaceuticals. Indeed, chemicals play a large role in raving to EDM. Concertgoers near the front of the stage are going mad. Robinson obliges the animated chaos, taking advantage of the technology at his disposal, and treating the amplification system as if it were aural IMAX and bombing ears with decibels. He mashes some Daft Punk, a seemingly requisite part of every deejay's production. But when will Robinson and his fellow EDM peers showcase the French pioneers' visual and sonic originality? (BG)

6:35 p.m.: A giant, synchronized mass of arms and hands waves side to side during the Shins' "Phantom Limb." The group's mellow, wordless refrains ("la la la la," "whoa-oh oh," "oh-whoa-oh whoa-oh") stick in the brain like caramel to teeth. Retooled, James Mercer's ensemble is bigger and brighter than before, and all the proverbial i's are dotted, all the t's crossed. The leader's voice nearly cracks when attempting extreme highs and crooning sentimental thoughts. Laidback guitars ripple, and despite the timely jangling passage or fuzz-distorted riff, the group's exchanges of pleasantries and parasol-strolling ditties seem too contained given its slot on a big stage. Effortlessness accounts for some of the band's appeal, but it would be nice to see Mercer and Co. give a gutsier performance. Who needs a lullaby early on a Friday night? (BG)

6:40 p.m.: A Passion Pit fan notices me scribbling in a notebook and advocates for a positive review. “They’re good outdoor music,” she says. It’s true. Passion Pit’s music does translate well on the big stage, giving a huge, easily distracted festival crowd plenty to look at and sing along with. But it’s an odd disconnect, one that must not be lost on singer Michael Angelakos. Many of his songs chronicle his struggles to maintain his personal equilibrium in the wake of being diagnosed bipolar as a teenager. In recent weeks, the bearded singer canceled a number of tour dates to focus on his mental health. The singer shows no ill effects as he stalks the stage, leaving his dress shirt and tie soaked in sweat. Angelakos hits high notes most people can only dream about spearing, and he writes layered songs brimming with hooks. He takes care to enunciate each word in his songs: “I'm so self loathing that it's hard for me to see/Reality from what I dream.” Yet the music defies that description, rising above all maladies to embrace perseverance, to proclaim the narrator’s resilience. It’s “good outdoor music,” certainly. But it’s also something more: a soul singer trying to heal himself -- and by extension others -- with his songs. (GK)

7:35 p.m.: As the sun gives way to dusk, Nero becomes the first artist at Perry's with the chance to maximize the potential of the various screens and blinding lights. Yet the London-based electronic team wastes the opportunity and retains a monotonous progression in line with its concoctions of dubstep, techno and drum-and-bass. Outside of vocalist Alana Watson briefly emerging to sing, Nero follows a pattern as predictable as staid verse-chorus-verse rock. Music throbs and rises to intense crescendos, fades and then reforms into towering clusters. Surprises? Limited, unless annoying compression of vocal phrases into chipmunk bleats counts as a positive. There's scant differentiation between the rousing passages; snippets of familiar tunes by the likes of Lil Wayne and the White Stripes punctuate the affair but lend to the impression that the display is little more than an anonymous manipulation of prerecorded tracks. Nodding their heads in approval and primarily staring down at their equipment, Daniel Stephens and Joseph Ray offer nothing in the way of visual stimulation. (BG)

8:05 p.m. A bell tolls, a bass guitar moans, and Ozzy Osbourne sings. “What is this that stands before me?” the former archnemesis of John Cardinal O’Connor intones with chilling deliberation. Black Sabbath – three-quarters of them, anyway – are back to reprise the doom-ridden, Beelzebub-baiting classics from the ‘70s. Osbourne sounds in good voice initially, slicing through Tony Iommi’s granite-hard guitar riffs and Geezer Butler’s nuclear-strength bass. He even lays down some credible blues harp on “Wizard.” But, as if to prove he isn’t lip-synching, Osbourne struggles to nail some of the high notes in “War Pigs.” No matter, Sabbath was never about sex appeal or perfection. They were dead-end working-class kids who had no use for the romanticism of the flower-power era, and instead peered into the abyss that awaits us all. The songs, which just happened to invent an entire genre of music, still sound magnificent, from “N.I.B.” to “Iron Man.” Iommi, who recently underwent cancer treatment, looks a little gaunt, but his playing is as fluid as ever. The only down side is that the band could not find a way to include drummer Bill Ward, who was originally scheduled to play Lolla but bailed when he couldn’t reach agreement with his old bandmates. He is replaced by former Rob Zombie drummer Tommy Clufetos, whose energy is welcome but who doesn’t quite have the cinder-block power and swing of Ward. (GK)

8:26 p.m.: Let the good times roll. M83 ends up playing slightly longer than its allocated time, riding waves of synthesizers and reverb-enhanced guitars to pop bliss. The group even flirts with jam-band tendencies but is careful to adhere to variation and a forward-driving pace. Who ordered that saxophone? No matter. Anthony Gonzalez and crew invoke blissful dreams and well-preserved memories with their ambient-streaked fare, compositions such as "Midnight City" providing a fitting soundtrack as the final traces of sunlight give way to darkness. (BG)

9:02 p.m.: At last. Perry's reaches full potential in the pitch-black, with a sensory overload of flashing lights and geometric shapes gracing screens and flat surfaces. Bassnectar treats the volume-bumping set as a scientific laboratory, churning out a futuristic assembly of beats, modified frequencies and re-jiggered samples. Amphetamine-spiked dubstep seems to be the year's preferred flavor among electronic fans, and the Santa Cruz deejay ups the ante by demonstrating how a slightly improvised approach can lead to absorbing contrasts. A fugue amid feverish rhythms? Why not? When you're dealing with that much firepower and illumination, anything goes. (BG)

9:32 p.m.: The Black Keys are all grown up. Having seemingly played at nearly every Lollapalooza since its reinvention, the band crawled its way up from smaller stages to headliner status. And with that graduation comes a "Spinal Tap"-worthy introduction that obscures the group behind a dense wall of fog and prompts front man Dan Auerbach to joke about it. Ah, mainstream success. As expected, the songs are as tight as a Tom Brady spiral and emerge with unjaded professionalism. The raggedness and loose commotion of the past are gone, and a bassist and keyboardist now help round out the duo's fare. Not that the changes are necessarily for the worse. "Strange Times" still uncoils and strikes at the heels; molasses-coated guitar lines on "Ten Cent Pistol" swerve and buzz. Drummer Patrick Carney and Auerbach know each other's moves in the same way an old married couple recognizes their mate’s habits. The Ohioans are solid, amicable and punchy, pleasing the fans with catchy devices and smoothing out the bluesy, rougher-around-the-edges bluster of the past. In other words, the more mature Black Keys are what a Lollapalooza headliner is supposed to be, nothing more, nothing less. (BG)

The Lollapalooza Music Festival kicks off Friday in Chicago, and the Tribune will have full coverage. If you aren't sure which bands to see on the festival's first day, allow Tribune music critic Greg Kot to offer up some picks for must-see acts: